# -*- coding: utf-8 -*-

import math

x1, y1, x2, y2 = map(float, raw_input().split())
dx = x2-x1
dy = y2-y1
print math.sqrt(dx*dx+dy*dy) import math math x1, y1, x2, y2 = map(float, raw_input().split()) x1 map(float, raw_input().split()) map float raw_input().split() ().split () raw_input split y1 x2 y2 dx = x2-x1 dx x2-x1 x2 x1 dy = y2-y1 dy y2-y1 y2 y1 print math.sqrt(dx*dx+dy*dy) math.sqrt math sqrt dx*dx+dy*dy dx*dx dx dx dy*dy dy dy x1, y1, x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) x1 y2 = map(float, raw_input().split()) map(float, raw_input().split()) y2 y1, x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) y1 x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) x2 dx = x2-x1 x2-x1 dx dy = y2-y1 y2-y1 dy
# -*- coding: utf-8 -*-

import math

x1, y1, x2, y2 = map(float, raw_input().split())
dx = x2-x1
dy = y2-y1
print math.sqrt(dx*dx+dy*dy)